Hi, <wta> how can I upload my icloud photos via iproperty website?

When I try to upload some photos to iproperty page, the gallery opened from the page only shows very little photos available for attaching. Izi because the photos that is backup to icloud doesn't show in it? If so how can I access to it? (I'm using iPhone 7p)

I also tried ticked the icloud photo sharing thing in settings, but still the same
Pls guide me if u will. Tyvm